Modified biochar activated persulfate for degradation of tetracycline

Tetracycline hydrochloride (TC) degradation was investigated utilizing hydrogen peroxide modified magnetic biochar (H2O2modified biochar, HMB) as an activator of peroxydisulfate (PDS), with a focus on assessing the impact of initial pH on TC degradation kinetics. The underlying reaction mechanisms and degradation pathways of HMB-activated PDS for TC degradation were elucidated through a series of experimental techniques, including quenching tests, electron paramagnetic resonance (EPR) spectroscopy for identifying active species, X-ray photoelectron spectroscopy (XPS) analysis, density functional theory (DFT) calculations, and liquid-liquid mass spectrometry (LC-MS) detection. Hydrogen peroxide modification significantly enhanced TC removal, achieving a removal rate of 83.9% under the specified conditions of TC concentration (20mg/L), PDS concentration (1mmol/L), and HMB dosage (0.5g/L). This efficacy surpassed that of PDS alone or the unmodified biochar system, albeit exhibiting a decrease in removal efficiency with rising pH levels. Quenching tests and EPR analyses unveiled both radical and non-radical pathways contributing to TC degradation, the active species mainly includes: SO·4− 、 iOH 、O2.- and 1O2. XPS analysis identified carbonyl (C=O) functionalities as the primary active sites responsible for TC degradation within the HMB/PDS system. Complementary DFT calculations were employed to quantitatively assess the contribution of C=O moieties to the HMB/PDS-mediated degradation process. Furthermore, LC-MS analyses coupled with DFT calculations delineated two distinct degradation pathways for TC, involving mechanisms such as deamidation, hydroxylation, demethylation, and dehydration ring opening. © 2024 Chinese Society for Environmental Sciences. All rights reserved.